Abstract: Objective　To determine the content of free amino acids（FAAs）in breast milk from mothers of infants with allergies who are exclusively breastfed，analyze the differences in FAA distribution characteristics between these mothers and those of non-allergic infants exclusively breastfed，and explore the mechanism of food allergy in the allergic infants and its significance in the optimization of breastfeeding strategies. Methods　Exclusively breastfed infants aged 0.5-6.0 months were selected， who visited the Outpatient Department of Pediatrics and the Department of Preventive Health Care of the First Affiliated Hospital of Kunming Medical University from September 2022 to May 2023. The infants were paired and divided into a non-allergic group（n=30）and an allergic group（n=30）based on the presence or absence of allergic manifestations. Breast milk samples were collected from the mothers of these infants.Tandem mass spectrometry（LC-MS/MS）was used for quantitative detection of FAAs in the breast milk samples. The differences in the contents of FAA between the two groups were analyzed and compared， and their statistical significance was explored. Results　The total amino acid content in the non-allergic group was higher than that in the allergic group. The contents of leucine（t=2.336，P=0.023）and ornithine（t=-2.93，P=0.005）showed statistically significant differences between the two groups（P<0.05），while no statistically significant differences were observed in the contents of other amino acids between the two groups（P>0.05）. Specifically，the leucine content in the non-allergic group was higher than that in the allergic group，and the ornithine content was lower in the non-allergic group than in the allergic group. Conclusion　In this study，the total amino acid content in the allergic group is lower than that in the non-allergic group，suggesting that the degree of protein degradation in breast milk of the allergic group may be lower，which may be associated with the mechanism of allergy development in exclusively breastfed infants. The higher leucine level in the non-allergic group may affect the infant’s immune regulation and intestinal barrier function，thereby reducing the risk of allergies.

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摘要： 目的　检测纯母乳喂养过敏婴儿母亲乳汁游离氨基酸的含量，分析其分布特征与非过敏婴儿母亲乳汁游离氨基酸差异，探讨过敏婴儿食物过敏机制及其在母乳喂养策略优化中的意义。方法　选取2022年9月至2023年5月昆明医科大学第一附属医院儿内科门诊及预防保健科年龄0.5~6.0月龄纯母乳喂养婴儿，按婴儿有无过敏表现配对分组，其中非过敏组（30例）、过敏组（30例），收集母亲乳汁样本。运用串联质谱技术对乳汁样本中游离氨基酸进行定量检测，比较分析两组间游离氨基酸含量的差异，并探讨其意义。结果　非过敏组氨基酸总量高于过敏组。亮氨酸（t=2.336，P=0.023）、鸟氨酸（t=-2.93，P=0.005）含量在非过敏组和过敏组间差异有统计学意义（P<0.05），其余种类氨基酸在两组间差异无统计学意义（P>0.05）。非过敏组亮氨酸含量高于过敏组，鸟氨酸含量低于过敏组。结论　过敏组氨基酸总量低于非过敏组，提示过敏组乳汁蛋白质降解程度可能更低，这可能与纯母乳喂养婴儿发生过敏的机制存在关联。非过敏组较高的亮氨酸水平，可能会影响婴儿免疫调节及肠道屏障功能，从而降低过敏发生风险。

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